Updated to initial implementation using cpp.

Main.h

@@ -0,0 +1,23 @@
+#include <iostream>
+#include <chrono>
+#include "Exercises.h"
+
+int main()
+{
+    while (true) {
+        // Input
+        char input;
+        cout << "Check(c), test(t) or quit(q) -> ";
+        cin >> input;
+        cout << endl;
+
+        // action
+        auto t1 = std::chrono::high_resolution_clock::now();
+        if (input == 'c') cout << "check result: " << Ex3(13195) << endl;
+        else if (input == 't') cout << "test result: " << Ex3(600851475143) << endl;
+        else  if (input == 'q') break;
+        auto t2 = std::chrono::high_resolution_clock::now();
+        auto duration_ns = std::chrono::duration_cast<std::chrono::microseconds>(t2 - t1).count();
+        cout << "Duration = " << duration_ns << " microseconds" << endl;
+    }
+}